License for python-grabbit updated from “MIT” to “MIT AND Unlicense”

[Ben Beasley]

The License field for python-grabbit has been updated from “MIT” to “MIT 
AND Unlicense” to reflect the _version.py file generated by Versioneer 0.29.

As described in 
https://github.com/python-versioneer/python-versioneer#license, the 
_version.py file generated by Versioneer is under the same license as 
Versioneer itself. Since Versioneer 0.24, this is Unlicense; before 
that, it was CC0-1.0, or in much older versions, a public-domain 
declaration represented as LicenseRef-Fedora-Public-Domain.